Thyroid Cancer Risk Is Not Increased in Diabetic Patients

OBJECTIVE: This study evaluated thyroid cancer risk with regards to diabetes status and diabetes duration, and with the use of anti-diabetic drugs including sulfonylurea, metformin, insulin, acarbose, pioglitazone and rosiglitazone, by using a population-based reimbursement database in Taiwan. METHODS: A random sample of 1,000,000 subjects covered by the National Health Insurance was recruited. After excluding patients with type 1 diabetes, 999730 subjects (495673 men and 504057 women) were recruited into the analyses. Logistic regression estimated the odds ratios (OR) and their 95% confidence intervals (CI) for independent variables including age, sex, diabetes status/duration, anti-diabetic drugs, other medications, comorbidities, living regions, occupation and examinations that might potentially lead to the diagnosis of thyroid cancer in various models. RESULTS: The diabetic patients had a significantly higher probability of receiving potential detection examinations (6.38% vs. 5.83%, P<0.0001). After multivariable-adjustment, the OR (95% CI) for diabetes status was 0.816 (0.652–1.021); and for diabetes duration <1 year, 1–3 years, 3–5 years and ≥5 years vs. non-diabetes was 0.071 (0.010–0.507), 0.450 (0.250–0.813), 0.374 (0.203–0.689) and 1.159 (0.914–1.470), respectively. Among the anti-diabetic agents, only sulfonylurea was significantly associated with thyroid cancer, OR (95% CI): 1.882 (1.202–2.947). The OR (95% CI) for insulin, metformin, acarbose, pioglitazone and rosiglitazone was 1.701 (0.860–3.364), 0.696 (0.419–1.155), 0.581 (0.202–1.674), 0.522 (0.069–3.926) and 0.669 (0.230–1.948), respectively. Furthermore, patients with benign thyroid disease or other cancer, living in Kao-Ping/Eastern regions, or receiving potential detection examinations might have a significantly higher risk; and male sex, hypertension, dyslipidemia, chronic obstructive pulmonary disease, vascular complications or use of statin, aspirin or non-steroidal anti-inflammatory drugs might be associated with a significantly lower risk. CONCLUSIONS: There is a lack of an overall association between diabetes and thyroid cancer, but patients with diabetes duration <5 years have a significantly lower risk. Sulfonylurea may increase the risk of thyroid cancer.